A popular method for error detection for digital signals is the Cyclic Redundancy Check (CRC). CRC works by treating the message string that is sent between a transmitter and a receiver as a single binary word. The single binary word is divided by a key word that is agreed upon by both the transmitter and the receiver ahead of time. The remainder that is left after dividing the single binary word by the key word is known as a check word. The transmitter sends both the message string and the check word to the receiver. The receiver then verifies the data by dividing the data by the key word. If the remainder, obtained by dividing the data by the key word, matches the check word, then the receiver can be sure that the data is indeed the correct message string from the transmitter.
In the context of CRC, key words are usually numbers and are presented in the form of polynomials whose coefficients are in the form of the binary bits of the key word. A popular key word is X16+X12+X5+1 known as the X25 standard. Key words will herein be referred to as polynomial key words.
CRC is often implemented in hardware that is specific to a given polynomial key word. A CRC that is implemented in hardware is herein referred to as a CRC generator. Thus, a system that has to verify data using various different polynomial key words will need a separate CRC generator that is dedicated to each distinct polynomial key word. For example, FIG. 1 is a block diagram that illustrates a CRC generator that employs a 3rd order polynomial key word, X3+X2+1.
In FIG. 1, exclusive-OR gates (XOR gates) 110, 112, and 116 are communicatively coupled to each other and to corresponding shift registers 102, 104 and 106. Input 101 is initially received at XOR gate 110. The output of the CRC generator in FIG. 1 is 118.
FIG. 2 is block diagram that illustrates a CRC generator that employs a 1st order polynomial key word, X1+1. In FIG. 2, XOR gates 210, and 212 are communicatively coupled to each other and to corresponding shift registers 202, and 204. Input 220 is initially received at XOR gate 210. The output of the CRC generator in FIG. 2 is 222.
A system with multiple CRC generators can be unwieldy and inefficient.
Based on the foregoing, it is clearly desirable to reduce the number of CRC generators in a given system.
It is further desirable to have a programmable CRC generator so that the CRC generator can be dynamically changed to accommodate different applications.